arctan(arctan(arctanh(x)))=x-2/3!*x^3+32/5!*x^5-944/7!*x^7+64640/9!*x^9...

A012233

arctan(arctan(arctanh(x)))=x-2/3!*x^3+32/5!*x^5-944/7!*x^7+64640/9!*x^9...

Terms

    a(0) =1a(1) =-2a(2) =32a(3) =-944a(4) =64640a(5) =-5881600a(6) =919673856a(7) =-172830523392

External references